An acoustic guitar has a hollow body forming a soundbox with a sound hole into the soundbox and a plurality of strings arranged over the sound hole. Some acoustic guitars are amplified by an external microphone, and some acoustic guitars include an electronic pickup device mounted within the soundbox.
For amplified hollow body guitars, acoustic feedback can be a problem. Acoustic feedback happens when an amplified soundwave from the guitar resonates a guitar front face or soundboard, and the guitar strings, which resonates within the hollow inside of the guitar body at certain frequencies. The resonating frequencies are amplified by the amplifier and when played through the loudspeakers in turn causes an increase in the resonating of the guitar in a feedback loop. The feedback loop cause an unpleasant buzz or hum sound.
To alleviate this problem, it is known to provide a cover over the sound hole which selectively reduces the open area of the sound hole to control acoustic feedback. The cover can be adjustable in that the open area of the sound hole can be effectively increased or reduced by manual manipulation.
U.S. Pat. No. 6,681,661 describes an adjustable cover member for the sound hole of a guitar. The cover enables complete or partial closure of the hole. The cover incorporates a base plate provided with two triangular openings. A circular adjustment plate is pivotally mounted on the base plate. The circular adjustment plate includes a pair of triangular openings of substantially the same size of the triangular openings in the base plate. When the triangular openings in the adjustment plate are rotated to register with the openings in the base plate, the openings provide a maximum open area through the sound hole. The plate can be manually rotated to selectively reduce the registration of the openings between the adjustment plate and the base plate to tailor the sound of the guitar and to reduce the interaction of the external loudspeakers and the sound waves resonating in the hollow body of the guitar. At one position the openings of the adjustment plate are completely out of registry with the openings in the base plate and the adjustment plate effectively closes the sound hole. U.S. Pat. No. 6,681,661 is herein incorporated by reference to the extent that it is not contrary to the present disclosure.
Other attempts at sound hole covers are disclosed in U.S. Pat. Nos. 4,394,830; 4,632,003; 5,883,322; and 9,646,581, all herein incorporated by reference to the extent that they are not contrary to the present disclosure.
The present inventor has recognized that if the sound hole cover is completely closed, acoustic feedback problems may be minimized or eliminated. However, this may create an unwanted side effect. If a guitarist is performing in front of a live audience, the amplified loudspeakers may be directed toward the audience and not toward the guitarist. The guitarist may not be able to hear his own playing to monitor his performance, particularly if other sounds on stage from other musical instruments overwhelms the unamplified acoustic sounds emanating from the guitar.
The present inventor has recognized the desirability of providing, for an amplified acoustic guitar with a soundbox and a sound hole, an adjustable closing device to reduce or eliminate unwanted acoustic feedback, while at the same time providing at least a small degree of sound to emanate from the sound hole.
The present inventor has recognized the desirability of an acoustic guitar having a sound hole closing device to prevent unwanted feedback but that also provides unamplified sound to the guitarist in an audible signal for stage-monitoring the guitarist's performance.
The present inventor has recognized the desirability of an acoustic guitar sound hole cover that was cost effectively manufactured, effective to prevent unwanted acoustic feedback, rugged in construction, and easily adjustable by the guitarist.